"Once you put on the pads and you take a hit and you fall on your knee and you get up - that's when you know you're ready to go," Lattimore, the 49ers' fourth-round draft pick, said today. "I mean, you can do all the agility drills, training drills, everything you want. But until you get hit, that's when you know."

Which means that it might be a year before Lattimore is certain he is 100 percent again.

While the 49ers rookie class has gone through full contact practices in pads the last two days, Lattimore was placed on the non-football injury list earlier this week. He is expected to remain on that list to begin the regular season, which would give the 49ers the option of activating him late in the season or shutting him down altogether.

Lattimore suffered a gruesome knee injury in October in which he tore multiple ligaments and dislocated the knee cap. He went through a grueling rehabilitation process to get ready for the draft. After the draft, Jim Harbaugh said the 49ers would slow that recovery down to make sure the knee fully heals. Lattimore said he understood and appreciated the 49ers' caution.

At the same time, he said he's made definite progress in the three months he's been with San Francisco. "Honestly, I feel the improvement every day," he said. "You get the running down, then you get agility. Then it translates to football after that. I honestly feel better every day."

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Another rookie, tight end Vance McDonald, got a chance to meet the man he will try to replace this season, Delanie Walker, at the rookie symposium in Los Angeles earlier this month. McDonald's greeting after shaking hands with Walker: "Hey, you're not a bad blocker."

That wasn't always the case. Walker, who was signed by Tennessee in free agency, was a wide receiver when the 49ers drafted him in 2006, and he's had to work hard to gain size and strength and become one of the better blocking tight ends - especially downfield - in the league.

McDonald said that will serve as good lesson for him. He did little in-line blocking at Rice and was split wide as a receiver one season. McDonald acknowledges that his ability to block will determine how much he sees the field this season. "You don't ever want to have one role," he said. " ... for me, I'd like to be known as being 50-50: You put him out wide, he's good out wide. You put him inside and run block, he's good inside."

MATTHEW BARROWS

Matt was born in Blacksburg, Va., and attended the University of Virginia. He graduated in 1995, went to Northwestern for a journalism degree a year later, and got his first job at a South Carolina daily in 1997. He joined The Bee as a Metro reporter in 1999 and started covering the 49ers in 2003. His favorite player of all time is Darrell Green.